1. Field of the Invention
The present invention relates to a running gear for an electric rolling stock which is capable of preventing electrolytic corrosion.
2. Description of the Related Art
FIG. 1 illustrates a conventional running gear of this type which is shown in, for instance, MITSUBISHI WN Drive (Catalog No. A-C7331-A, issued by Mitsubishi Electric Corporation in November 1983). As shown in FIG. 1, paired wheels 2 are secured to both ends of axles 3 and are disposed in contact with tracks 1. The axles, consisting of a pair of axles 3, support a bogie transom 4 via associated axles boxes (none of which are shown). A pair of traction motors 5 are mounted at predetermined locations on the bogie transom 4, and their output shafts are disposed substantially in parallel with the axles 3. A reduction device 6 is mounted on each of the axles 3 with an end portion thereof supported by the bogie transom 4. Each of the traction motors 5 and each of the reduction devices 6 are coupled by means of a gear coupling 10. A grounding device 8 is provided on each reduction device 6 in such a manner as to be capable of coming into contact with the corresponding axle 3. Each of the grounding devices 8 is connected to the bogie transom 4 via a connecting wire 9.
With such a conventional running gear, when the traction motors 5 are started, the rotation of each traction motor 5 is transmitted to the corresponding reduction device 6 via the gear coupling 10, the speed of rotation is reduced to a predetermined speed by the reduction device 6, the axle 3 and the paired wheels 2 are rotated at the speed, and the electric rolling stock runs on the tracks 1 as the wheels 2 run thereon.
At this time, if, for instance, another vehicle runs near the rolling stock, return current may flow from the tracks 1 to some of the members of the rolling stock such as the bogie transom 4. In such a case, the return current flows through, for instance, the following path: one track 1.fwdarw.wheels 2.fwdarw.axles 3.fwdarw.grounding devices 8.fwdarw.connecting wires 9.fwdarw.bogie transom 4.fwdarw.connecting wires 9.fwdarw.grounding devices 8.fwdarw.axles 3.fwdarw.wheels 2.fwdarw.the one or the other track 1.
The above-described arrangement of the conventional running gear, however, encounters a problem in that, when the contact resistance of the grounding devices increases due to such factors as dust and moisture introduced into the grounding devices, the return current may flow from the tracks 1 to the bogie transom 4 through the reduction devices 6, the gear coupling 10, and the traction motors 5. This flow of the return current may adversely affect some of the component parts, such as bearings and gear surfaces, of these members by causing electrolytic corrosion thereof.